Kyle Weatherholtz noted an obvious problem; renewable energy sources, like the wind and the sun, are intermittent, and asked rhetorically, “But, what if there was a way to store energy when there is a surplus and kick it back out when there is a lag in production or increased demand?”
As this blog previously had done, he discovered development by Beacon Power:
I recently learned about a company called Beacon Power that developed a gnarly flywheel energy storage system. The technology seems pretty simple and has probably been around for sometime but I haven’t seen much it being utilized with renewable energy—where it would be most valuable.
Essentially, what makes the storage capabilities of a flywheel system sustainable is the ability to store energy in kinetic form as opposed to chemical. A wheel spins on a shaft holding energy that can be used when power is lost. An electronics module allocates energy to the motor to drive the flywheel and when power is lost, this motor becomes a generator and sends compatible energy to the grid.
Beacon flywheels are specifically designed to withstand extreme rotation speeds that allow for the storage of large quantities of energy. They have a process called Smart Energy Matrix, that is a system on interconnected higher-power flywheels for specific use with utility grade operations.
As renewable energy is further and further embraced, we will likely see more on energy storage systems like the flywheel.
“The Lone Star state has installed wind power close to 5,000 megawatts which translates to enough electricity to power a million homes. The huge turbines, scattered across wide open spaces, conjure up more progressive feelings compared to those generated at the sight of oil rigs or smoke stacks; they are feelings of a changing world, a cleaner world,” writes Weatherholtz.
As a follow-up on investments in wind and efficiency in the United States, this blog relays information from a post by James Fraser. In the Energy Blog he reports that commercial projects are now underway that use:
- Flow batteries,
- CAES (Compressed Air Energy Storage),
- Thermal energy storage,
- Pumped hydro, and
- Sodium sulfur batteries for energy storage in connection with renewable energy projects.
American Electric Power (AEP) is also using NaS batteries in a couple of their systems, but not in connection with wind power. While not enough experience has been gained with any of these technologies to make any decision as to which technology is best under what conditions, pumped hydro and sodium sulfur batteries are the most well proven and thus seem to be the first choice of electric utilities. Thermal storage is gaining acceptance for use with thermal solar systems.
A NaS cell “consists of liquid (molten) sulfur at the positive electrode and liquid (molten) sodium at the negative electrode as active materials separated by a solid beta alumina ceramic electrolyte. The electrolyte allows only the positive sodium ions to go through it and combine with the sulfur to form sodium polysulfides.”
In partnership with the University of Minnesota, the National Renewable Energy Laboratory and the Great Plains Institute, Xcel Energy soon will begin testing a sodium-sulfur battery storage system. The developers will demonstrate the ability of the 1MW system to store wind energy, then dispatch it to the electricity grid as needed.
Fully charged, the batteries could power 500 homes for six and one-half hours. Xcel Energy will purchase the batteries from NGK Insulators, Ltd. that will be an integral part of the project. The sodium-sulfur battery is commercially available and versions of this technology are already being used in Japan and in a few US applications, but this is the first U.S. application of the battery as a direct wind energy storage device.
The 50-kilowatt battery modules, 20 in total, will be roughly the size of two semi trailers and weigh approximately 60 tons. They will be able to store about 6.5 megawatt-hours of electricity, with a charge/discharge capacity of one megawatt. When the wind blows, the batteries are charged. When the wind calms down, the batteries can be used to supply energy to the grid as needed.
"Energy storage is key to expanding the use of renewable energy. This technology has the potential to reduce the impact caused by the variability and limited predictability of wind energy generation."– Dick Kelly, Xcel Energy chairman, president and CEO.
The project will take place in Luverne, Minn., with the battery installation beginning this spring adjacent to a nearby 11-megawatt wind farm owned by Minwind Energy, LLC. Testing will begin in October and is expected to last up to two years.